AU
B168500

DTC B168500 indicates an invalid configuration fault in A/C System Circuit 1 (specifically the electric compressor drive circuit) — Atto 8

Safety System

DTC B168500 indicates an invalid configuration fault in A/C System Circuit 1 (specifically the electric compressor drive circuit).

On BYD Qin PRO models, 'Circuit 1' typically refers to the electric A/C compressor high-voltage drive and LIN communication circuits. 'Invalid configuration' indicates mismatched communication parameters between the HVAC ECU and the compressor control unit, an unconfigured LIN address, or abnormal circuit topology recognition.

This fault completely disables the A/C cooling function and may limit vehicle power output.

Although some sources classify this as an SRS fault, the BYD fault code structure (B16xxxx) categorizes it under the body HVAC system, with no direct relation to the airbags.

4
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Electric compressor LIN line communication fault (open circuit, short circuit, or high contact resistance)
  • 2Failure to perform control unit coding/parameter configuration after replacing the electric compressor.
  • 3Air conditioning controller (HVAC ECU) software version outdated or internal fault.
  • 4Faulty electric compressor control unit or loss of internal parameters.
  • 5Compressor high-voltage interlock circuit or low-voltage power supply circuit fault
What To Do
  • 1
    Connect the diagnostic tool, enter the HVAC system, read the complete fault codes and freeze frame data, and check 'Compressor Status' and 'LIN Communication Status' in the data stream.
  • 2
    Check the front compartment electric compressor wiring harness connectors (especially the high-voltage plug and low-voltage signal plug) for looseness, water ingress, oxidation, or burning.
  • 3
    Use an oscilloscope to measure the LIN line waveform (normal: dominant level 0V, recessive level 12V, baud rate approx. 10.4kbps) and check for a short to ground or power.
  • 4
    Measure the compressor low-voltage power supply (12V) and ground, and check the high-voltage interlock circuit for continuity.
  • 5
    If the compressor was recently replaced, use the diagnostic tool to perform the 'Replace electric compressor' or 'Control unit coding' function, and enter the correct configuration parameters based on the part number.
  • 6
    Upgrade the HVAC controller software to the latest version (specific software patch applicable to 2018-2019 Qin PRO models).
  • 7
    If the above steps fail, replace the electric compressor assembly or air conditioning controller and reconfigure.
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM: B168500 caused by missing coding after compressor replacement

✓
A 2019 Qin PRO DM received a replacement electric compressor due to abnormal noise. After installation, the A/C did not cool. No warning lights appeared on the instrument panel, but the HVAC system stored DTC B168500. Technicians found the new compressor had not been configured as a LIN node. Using the VDS2000 diagnostic tool, they entered 'Special Functions' > 'Replace Electric Compressor', input the part number from the new compressor label (e.g., BC28-XXXX), and executed the coding. The fault code cleared automatically and the air conditioning returned to normal.
BYD DTC AI Analysis

Loose LIN connector caused intermittent B168500

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2018 Qin Pro EV owner reported the air conditioning intermittently cut out while driving, resuming after a restart. Scan tool detected stored DTC B168500. Found the low-voltage connector (4-pin) for the front electric compressor had a broken internal locking tab, causing poor contact on the LIN line (typically pin 3). Repaired the harness connector, replaced the connector housing, and secured the harness against vibration. Fault has not recurred.
BYD DTC AI Analysis

Internal fault in the HVAC controller caused a circuit configuration error

✓
After wading through water, a 2019 Qin Pro petrol variant lost all air conditioning. DTC B168500 stored and could not be cleared. Inspection of the compressor and wiring showed normal operation, but the LIN bus voltage measured 0 V continuously. Disconnecting the compressor connector did not restore normal LIN voltage, indicating a failed LIN transceiver inside the AC controller. Replaced the HVAC controller assembly, performed online configuration and temperature motor self-learning, and resolved the fault.
BYD DTC AI Analysis

Invalid configuration due to software version mismatch

✓
A 2018 Qin PRO DM logged DTC B168500 after a system update at the dealership. A TSB search revealed a compatibility issue between the early HVAC software and new compressor control logic on this model. The tech downloaded a specific patch from the BYD after-sales system and downgraded the AC controller software to the stable version (or upgraded to the corrected release). The DTC cleared and the AC now works normally.
Other Atto 8 Fault Codes
B1108For the BYD Song MAX (2017–2019), DTC B1108 indicates a short circuit in the PM2.5 air quality detection module (dust sensor) or its wiring harness. The sensor uses laser scattering to detect in-cabin and outside PM2.5 concentrations and transmits data to the HVAC ECU via the LIN bus or an analog signal. Short circuit conditions include: 1) Sensor power supply wire (+5V/+12V) shorted to ground 2) Signal wire shorted to power or ground 3) Short circuit in the sensor's internal photoelectric detection circuit This fault prevents the automatic climate control from switching between fresh air and recirculation based on air quality. The system enters fail-safe mode (typically forced recirculation). Severe short-circuit current can destroy the HVAC ECU sampling circuit. The system classifies this as a Level 3 severe fault and restricts vehicle operation to prevent electrical fires or controller damage. For other BYD models (such as the Qin EV, E5, and Song DM), B1108 indicates a driver-side sunload sensor fault, reflecting differences in DTC definitions across models.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
Data confidence: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.